10.5” 14 bolt disk brakes with OEM park brakes

[57taskforce]

I will soon be putting bigger tires under my K20. I’ve decided to swap to rear disks on my 14 Bolt. As we’ve all seen that there are several ways to put disk brakes on a full floating 10.5” 14 bolt. Most involve using pre fabricated weld on caliper brackets, with 73-87 K20 front rotors and a few different caliper options. While relatively inexpensive, the huge draw back to these setups is the huge lack of a reliable parking brake setup. The Cadillac Eldorado calipers are an option for the park brakes but they are not known to be overly strong or reliable for a truck application.

The following is a 14 bolt disk swap done my way using all off the shelf GM parts for the swap from a late model axle. There seems to be very little definitive info on this swap online, pirate has a thread or two and few of the other 4x4 sites do as well but they don’t contain the most clear info or pictures, more often than not the info I found online was mostly reasons it can’t be done. I didn’t use any internet info in this swap, I just got the axles sided by side and started building. I will outline in this thread how I pulled it off. This is not a direct bolt on swap, or likely even the most cost effective swap, but it will provide an effective park brake setup and brakes designed for an HD truck.
The axle I’m going to be installing the disks on came from an ‘89 V30 square body cab and chassis, it is the newer style housing with the extra ribbing in the center section of the housing. This axle had 13 inch inboard mounted drums.(more on slip off drums to come)

I acquired all my swap parts from a 2005 Silverado 2500HD 6.0 10.5” 14 bolt axle. Note that this information is only confirmed using the brake parts from the 3/4-1ton 6.0 non dually trucks with the 10.5” 14 bolt disk brake axle with drum in hat. The 11.5” 14 bolt that is found in duallys and duramax/8.1 trucks is not the same axle as the 10.5” we all know and love. The 10.5” axle is still produced today by AAM and is 90% the same as the original from 1973. The major differences in the modern axles are the widths, spindles, hubs, and brakes.

Here’s a picture of the complete ‘05 disk axle before tear down. I don’t have any of the cab and chassis axle before I tore into it, but anyone reading this has likely seen many 14 bolts with drum brakes.

[57taskforce]

There’s a few variables that will come into play depending upon which variant of 14 bolt you are converting. If you’ve got a cab and chassis dually like me you’ll note the drum brake backing plate mount flanges are several inches inward of the ends of the spindles because of the narrow wheel mount surface of the cab and chassis. With this axle setup, you don’t HAVE to remove the drum brake flanges if you don’t want to, they will not interfere with disk setup. If you’ve got a single wheel axle, those will very likely have to be removed. It’s worth noting that the axle I’m building is being converted to single wheel in the process of the brake swap. If you’ve got a normal dually axle I’m not exactly sure if you’ll have to remove the flanges or not, I would guess that you would but can’t confirm.

Slip on drums: some ‘90s trucks came with slip on drums that don’t require the removal of the hub to take the drums off. The way I’m going about this swap will not work with those axles because they use a different spindle/hub. However, the swap on one of those axles will likely be easier because I believe you’d be able to use the later model disk brake hubs as well as the brake parts making so all you'd have to do is change to 9/16” studs and then get the disk brake backing plate flanges made and install everything onto the axle. You may also be able to use the 90’s slip on hubs with the slip on rotors from the disk brake axle but they will likely require some machine work to center the rotors onto the hubs. This will make more sense as this progresses and I’ll do my best to highlight what I mean by this as we go.

What I did first was strip both of my axles of their hub and brake parts and compare spindles and hubs between the two as seen below. The disk brake axle has a shorter spindle than the inboard mounted drum brake axle. This forced me to mount the brake rotor behind the ‘89 hub just like the original drum was mounted. If I had tried to make it a slip on rotor setup, because of the longer spindles the the backing plate flange would have to be mounted where the axle tube necks down to the spindle. This will not work. This is where the slip on drum rotors will differ, they have the shorter spindle that the disk brake axles have which I believe would allow you to put it together as a slip on rotor setup.

Here’s a few pictures. First one of the two axles side by side, the disk brake axle is in the rear. Next a picture comparing the spindles of the two. Next is the disks mocked up to the drum brake axle with single wheel hubs.
Last is more mock-up, the backing plate/caliper mount is just resting on the axle tube and the caliper is resting on a Jack stand to get the approximate height and positioning of where the backing plate flanges will be mounted up. At this point I knew the swap would work with the right parts and machine work.

[57taskforce]

Next I’ll get into specifics on the hubs and rotors. In order to properly center the rotor to the hub, the late model hubs have a boss machined into them that is the same diameter as the inside of the center of the rotor. I had the back side of the ‘89 drum brake hubs turned down .02 deep with an outside diameter that matches the center of the rotor.. At this point I had a friend who owns a big industrial machine shop we use at work make me up some backing plate mount flanges. These flanges were cut on a water jet and finished on a CNC mill. They are cut from 3/4” plate and have a boss built into the outside of them to center the backing plate/caliper mount. He used the backing plate/caliper mounts as a guide and had the centers cut for the slightly smaller ‘89 14 bolt axle tubes.(the factory disk axles have slightly larger Dana 70 spec axle tubes) They fit over the tubes snug, but not a press fit, to keep them centered on the tubes. As you’ll see in the last picture below, the drum brake flange is a square and the disk brake flange is more of a trapezoid. The trapezoid being considerably larger than the square in this case. In short the drum brake flanges will not work to mount the disk brake backing plate. Here’s some pictures of the hubs, backing plates and flanges.

Picture one and two shows the boss machined into the hub to center it to the rotor. In picture 1 the knife blade is resting on the new boss. The boss that is about 1/4” above the tip of the knife is the original used to center the brake drum. Notice the rotor has a bigger center diameter than the drum did.

The second picture shows the rotor resting and centered on the now machined hub. The lug studs will press into the rotor and hub from this side to pin the rotor to the hub.

The third and fourth pictures show the newly machined backing plate flange, and the backing plate/caliper mount. Notice how the flange has the boss machined into it to center into the recess that is factory machined into the center of the backing plate.

[57taskforce]

Now I’ll start putting it all together to weld the flanges on.. I started by installing the new backing plate flange with the backing plate centering boss facing the spindle as seen above. Next the backing plate without the upper caliper mount, can be bolted up to the flange. The rotor and hub will go next. Install the axles. Then the upper caliper bracket with pads installed and then last the caliper.

You’ll first be setting the caliper angle/height. Really, you can position the caliper wherever you like, as long as the bleeder is on top. I set mine in the factory location, facing forward and centered. Once you get the caliper angles where you want them, you’ll start setting the depth of the caliper and parking brake shoes in relation to the rotor. It’s critical that you don’t mount the caliper/backing plate too deep as the backing plate will rub the rotor if you do. I shot for about a 3/8” gap between the dust shield and the rotor all the way around.

In order to do this, move the whole caliper assembly in and out a little bit at a time until the caliper and park brake shoes move freely on/in the rotor. It will take a little bit of feel and listening to the pads/shoes drag on the rotor but you’ll know when you have it right. I put both sides together, then I adjusted each side until I could turn the pinion yoke by hand and have the least drag possible on both rotors. When correct they will both spin freely by hand or with the yoke and you will barely hear/feel any drag on the rotors. You’ll know when it’s right. Because the backing plate flanges are the same diameter as the tubes, they are self aligning side to side, so all I had to adjust was the depth of the flange if that makes sense. Once I had everything placed where I wanted it I tacked each side up in 4 places, 12,3,6 and 9 o,clock. I disassembled everything for final welding so as not the have excess weight/leverage on the flange that could move it around while being welded in.

Below is a picture sequence on the assembly process. You’ll notice in the last picture, I had a weld bevel machined into the back side of the flanges, a small detail that I felt is worth noting.

[57taskforce]

Once you get the backing plate mount flanges welded to the axle, now is a good time paint or do whatever other things you may need like replace bearings, seals, studs, calipers, rotors etc. Put it all back together one last time and your all set. I haven’t installed the axle in my ‘72 K20 because I’m not to that part of my build yet. When I get to that point I will address park brake cables, plumbing and 4 wheel disk master cylinder Choices along with anything else that comes up. Another thing worth noting on the hub seals is that GM has a much better updated seal design in the late model axles. I use this seal anytime I replace one in the older style axles. It’s a 2 piece design with a built in wear sleeve for the spindle and it works quite well. I will link to it at the bottom of this page. Also there are two types of hub nuts/retainers. My axle has the single hub nut with the key stock and circle clip that holds it all together. The other style is 2 hub nuts that jam together with a locking tab ring in between them. For hub nut torque I always have set the inner nut to 50 ftlbs while rotating the hub then backed off the nut and re torqued to 35ftlbs. Then add which ever locking mechanism style your axle has. If pictures are needed of the two different styles I can add them.

If interested in this swap, the cheapest route is likely to find a complete factory disk axle and rob all the brake parts off of it. I was fortunate enough to get 2 of these axles from work, for pretty cheap. They came from wrecked company trucks that were going for scrap. I was able to sell both the axles less the brake parts for 250 and 350. So If you do buy a complete axle you can likely make some of your money back if you don’t have a use for the axle. Another viable option would probably be a pick n pull for the brake parts only. Below I will attach a few pictures of the swap complete on stands, as well as the backing plate flange welded to the axle. I hope to swap it into my truck this spring. If anyone has any questions or if something is not clear post it here and I’ll see what I can do to help.

[57taskforce]

Reserved for instal, plumbing and parking brake cables

[57taskforce]

Reserved for install, plumbing and parking brake cables

[v30crewcab]

Interesting way to do it. I'm curious why you didn't just use the newer axle in the truck? that's what I did on mine. works great. just had to move the spring pads and it worked. they are a nice brake setup.

[57taskforce]

I figured that question would come up haha. There’s a couple reasons I didn’t. First I didn’t want to have to mess with moving perches...again.(I did it on the current 14 bolt that’s in my truck) The K30 square body 14 bolt perches are the same width as 67-72 so all I’ll have to do is move 1 shock mount. Second I wanted to keep the axle width the same. The later axles are a couple inches wider overall. Third, I wanted to be a little different.

[v30crewcab]

cool. I used a 02 silverado rear, it was only an inch wider overall.

[57taskforce]

I did notice the later hubs mount the wheel in a slightly different spot as compared to the old style hubs, so I’m not totally surprised if it was only 1”. I measured hub to hub, not wms to wms. The other part I failed to mention is I’ve got 4:11’s in my front 60 and both the late model axles had 3:42 and 3:73’s. I really wasn’t wanting to get new gears and set them up. How did you go about setting up your brake cables?

[v30crewcab]

the cables tied right into my stock pedal cable, I just used a piece of 1/4 allthread in between two cable hooks and added 6" to the length and it works great. running the 02 silverado hd cables.
the new rear had 4.10's, but its so easy to setup 14b gears I put a whole different setup in mine to make it 3.73. I had extra carriers,etc, so just a matter of throwing them in and setting them up to the case.

[Richard]

Understand you went the way you did. Kudos to the work you put in. Went a hopefully somewhat easier route with an AAM 11.5 that already has disk brakes. Is the same width as a Chevy front axle.